A variable valve mechanism 90A of a first conventional example shown in FIG. 13A and a variable valve mechanism 90B of a second conventional example shown in FIG. 13B switch between a coupled state where an input arm 92 and an output arm 93 are coupled together and an uncoupled state where the input arm 92 and the output arm 93 are uncoupled from each other. Each variable valve mechanism 90A, 90B includes lost motion springs 95 that bias the input arm 92 against a cam when the variable valve mechanism 90A, 90B is in the uncoupled state.
Specifically, in the variable valve mechanism 90A of the first conventional example (Patent Document 1) shown in FIG. 13A, the output arm 93 (outer arm) has slot holes 93a. A roller pin 97 is attached to the input arm 92 (inner arm) to axially support a roller 98. The roller pin 97 extends from the input arm 92 and through the slot holes 93a and projects laterally from the output arm 93. The roller pin 97 has spring retaining portions 97a in the projecting portions thereof, and extended portions 95a of the lost motion springs 95 are retained on the spring retaining portions 97a. 
In the variable valve mechanism 90B of the second conventional example (Patent Document 2) shown in FIG. 13B, extended portions 95b of the lost motion springs 95 are located in inter-arm clearances g between the input arm 92 (inner arm) and the output arm 93 (outer arm). Spring retaining portions 92b on which the extended portions 95b of the lost motion springs 95 are retained are formed in the upper part of the input arm 92 so as to extend in the inter-arm clearances g and project upward from the inter-arm clearances g.